Ptyalin acts upon

Options

A. Fats
B. Proteins
C. Lipids
D. Starch

Explanation

**Step-by-Step Solution:**

1. **Identify the Enzyme**: The question asks about "Ptyalin". It is important to recognize that Ptyalin is another name for salivary amylase.

2. **Location of Action**: Salivary amylase (Ptyalin) is produced in the salivary glands and is present in saliva.

3. **Function of the Enzyme**: The primary function of salivary amylase is to initiate the digestion of carbohydrates, specifically starch.

4. **Substrate of the Enzyme**: The substrate that salivary amylase acts upon is starch. When starch comes into contact with salivary amylase, it is broken down into simpler sugars.

5. **Conclusion**: Therefore, the correct answer to the question "Ptyalin acts upon" is starch.

**Final Answer**: Ptyalin acts upon starch.

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